Question

如何获取max average sal中的employee table;

我有

工作，deptno和sal。

我用它来查询：

select max(avg(sal))
from emp
group by job;

但它不起作用。

Answer 1

我尝试将您的表创建为：

mysql> SELECT * FROM emp;
+------+--------+-------+
| job  | deptno | sal   |
+------+--------+-------+
| SSD  |      1 | 58000 |
| SD   |      1 | 20000 |
| GD   |      1 | 35000 |
| AO   |      2 | 40000 |
| AhO  |      2 | 25000 |
| AhO  |      2 | 55000 |
| SSD  |      1 | 68000 |
+------+--------+-------+
7 rows in set (0.00 sec)

我运行你的查询，所以我得到了：

mysql> select max(avg(sal)) from emp group by job;
ERROR 1111 (HY000): Invalid use of group function

那是因为你已经嵌套了两个聚合函数。

要解决您的问题，我已更改您的查询，如下所示：

SELECT 
    job, 
    AVG(sal) AS average_salary
FROM emp 
GROUP BY job
ORDER BY average_salary DESC
LIMIT 1;

+------+----------------+
| job  | average_salary |
+------+----------------+
| SSD  |     63000.0000 |
+------+----------------+

Answer 2

不是将max（）函数应用于avg（）。尝试引入按工作分组的所有员工的avg（）。

 SELECT Avg(sal) AS avg_sal
     FROM   emp
     GROUP  BY job;

然后将max（）函数应用于子查询。

 SELECT Max(avg_sal)
    FROM   (SELECT Avg(sal) AS avg_sal
    FROM   emp
    GROUP  BY job) AS sub_tab;

如何使用mysql获得最大平均值？

2 个答案: